I got this email over the weekend. Maybe someone here has some insight?
I believe you were the person I was talking with before. If not, could you direct me to a better source to answer this question?
Just purchased a pristine looking Altair 8800 (not the "a", not the "b", but the original). After replacing a bum capacitor, I have the fan working and the lights are on. As I test the power supplies and the bus voltages, ground seems to be ground, the +16V and the -16V are fine, but the 5V DC is almost 12 V (the connectors on each of the bus slots that are on the opposite end of the ground). I have 2 X 4K static Ram and 1 X 16K static Ram but the memory addresses don't light up. All the data lights are lit, like I have no memory attached. But it may be that none of the boards will like having a 12 V DC where they expect to see a 5V. I went back to the power supplies and found them all delivering the appropriate voltages except for one. The top most power supply in the chassis is delivering 12 Volts instead of the listed 8 volts.
Couple of questions:
1) Is the 50% over listed voltage potentially the reason why I am getting 12 volts on the top most bus connector and not 5?
2) Do you know where the supposed 8 volts from the power supply gets converted to 5 volts on the bus? or is "5" volts really just the 8 volts from the power supply?